Effects of estrogen replacement therapy on serum lipid values and angiographically defined coronary artery disease in postmenopausal women

Hormone Therapy in Menopause: Concepts, Controversies, and Approach to Treatment

Hormone therapy (HT) is an effective treatment for menopausal symptoms, including vasomotor symptoms and genitourinary syndrome of menopause. Randomized trials also demonstrate positive effects on bone health, and age-stratified analyses indicate more favorable effects on coronary heart disease and all-cause mortality in younger women (close proximity to menopause) than in women more than a decade past menopause. In the absence of contraindications or other major comorbidities, recently menopausal women with moderate or severe symptoms are appropriate candidates for HT. The Women's Health Initiative (WHI) hormone therapy trials-estrogen and progestin trial and the estrogen-alone trial-clarified the benefits and risks of HT, including how the results differed by age. A key lesson from the WHI trials, which was unfortunately lost in the posttrial cacophony, was that the risk:benefit ratio and safety profile of HT differed markedly by clinical characteristics of the participants, especially age, time since menopause, and comorbidity status. In the present review of the WHI and other recent HT trials, we aim to provide readers with an improved understanding of the importance of the timing of HT initiation, type and route of administration, and of patient-specific considerations that should be weighed when prescribing HT.

Exercise modulates the aortic renin-angiotensin system independently of estrogen therapy in ovariectomized hypertensive rats

The renin-angiotensin-system is an important component of cardiovascular control and is up-regulated under various conditions, including hypertension and menopause. The aim of this study was to evaluate the effects of swimming training and estrogen therapy (ET) on angiotensin-II (ANG II)-induced vasoconstriction and angiotensin-(1-7) [ANG-(1-7)]-induced vasorelaxation in aortic rings from ovariectomized spontaneously hypertensive rats. Animals were divided into Sham (SH), Ovariectomized (OVX), Ovariectomized treated with E2 (OE2), Ovariectomized plus swimming (OSW) and Ovariectomized treated with E2 plus swimming (OE2+SW) groups. ET entailed the administration of 5μg of 17β-Estradiol three times per week. Swimming was undertaken for sixty minutes each day, five times per week. Both, training and ET were initiated seven days following ovariectomy. Forty-eight hours after the last treatment or training session, the animals' systolic blood pressures were measured, and blood samples were collected to measure plasma ANG II and ANG-(1-7) levels via radioimmunoassay. In aortic rings, the vascular reactivity to ANG II and ANG-(1-7) was assessed. Expression of ANG-(1-7) in aortic wall was analyzed by immunohistochemistry. The results showed that both exercise and ET increased plasma ANG II levels despite attenuating systolic blood pressure. Ovariectomy increased constrictor responses to ANG II and decreased dilatory responses to ANG-(1-7), which were reversed by swimming independently of ET. Moreover, it was observed an apparent increase in ANG-(1-7) content in the aorta of the groups subjected to training and ET. Exercise training may play a cardioprotective role independently of ET and may be an alternative to ET in hypertensive postmenopausal women.

Sagunja-Tang Improves Lipid Related Disease in a Postmenopausal Rat Model and HepG2 Cells

The present study was conducted to investigate the effect of Sagunja-tang on the lipid related disease in a rat model of menopausal hyperlipidemia and lipid accumulation in methyl-β-cyclodextrin-induced HepG2 cells. In in vivo study using menopausal hyperlipidemia rats, Sagunja-tang reduced retroperitoneal and perirenal fat, serum lipids, atherogenic index, cardiac risk factor, media thickness, and nonalcoholic steatohepatitis score, when compared to menopausal hyperlipidemia control rats. In HepG2 cells, Sagunja-tang significantly decreased the lipid accumulation, total cholesterol levels, and low-density/very-low-density lipoprotein levels. Moreover, Sagunja-tang reversed the methyl-β-cyclodextrin-induced decrease in the protein levels of critical molecule involved in cholesterol synthesis, sterol regulatory element binding protein-2, and low-density lipoprotein receptor and inhibited protein levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase as well as activity. Phosphorylation level of AMP-activated protein kinase was stimulated by Sagunja-tang. These results suggest that Sagunja-tang has effect on inhibiting hepatic lipid accumulation through regulation of cholesterol synthesis and AMPK activity in vitro. These observations support the idea that Sagunja-tang is bioavailable both in vivo and in vitro and could be developed as a preventive and therapeutic agent of hyperlipidemia in postmenopausal females.

Palmiwon attenuates hepatic lipid accumulation and hyperlipidemia in a menopausal rat model

OBJECTIVE

We examined the phytoestrogenic effects of palmiwon on breast carcinoma, lipid accumulation in methyl-β-cyclodextrin-induced HepG2 cells, and lipid-related diseases in a rat model of menopausal hyperlipidemia.

METHODS

E-Screen assay was used to screen for phytoestrogens, especially those with antiestrogenic activity, in MCF-7 cells. Oil Red O staining and intracellular cholesterol analyses were used to quantify cellular cholesterol levels. 3-Hydroxy-3-methyl glutaryl coenzyme A reductase assay was used to measure enzyme activity. The levels of phosphorylated adenosine monophosphate-activated protein kinases and products of genes involved in cholesterol synthesis were measured by Western blot analysis. Thirty rats were either ovariectomized or sham-operated and randomly assigned to four groups (n = 5)-Sham, OVX, OVX-SV, or OVX-PMW (50, 150, or 450 mg/kg) group-for 8 weeks. A number of targets associated with lipid-related diseases were examined to confirm the estrogenic effects of palmiwon.

RESULTS

Palmiwon showed antiestrogenic activity in MCF-7 cells. Palmiwon decreased lipid accumulation, total cholesterol levels, and low-density lipoprotein/very-low-density lipoprotein levels in HepG2 cells. Moreover, palmiwon reversed the effects of methyl-β-cyclodextrin on cholesterol synthesis regulators and inhibited the activity of 3-hydroxy-3-methyl glutaryl coenzyme A reductase. Phosphorylation of adenosine monophosphate-activated protein kinase was stimulated by palmiwon. In ovariectomized rats, palmiwon reduced retroperitoneal and perirenal fat accumulation, serum lipids, atherogenic index, cardiac risk factor score, intima-media thickness, and nonalcoholic steatohepatitis scores.

CONCLUSIONS

These results indicate that palmiwon inhibits lipid accumulation without estrogenic activity in the breast. Therefore, palmiwon may have potential as a therapeutic agent for the treatment of hyperlipidemia in postmenopausal women.

Flaxseed reverses atherosclerotic lesion formation and lowers lipoprotein(a) in ovarian hormone deficiency

OBJECTIVE

The incidence of cardiovascular disease dramatically increases during menopause, and postmenopausal women seek natural alternatives to hormone therapy. Flaxseed can slow the progression of atherosclerotic lesion formation; however, it is not known whether it can reverse formation that has already occurred.

METHODS

Seventy-two female Golden Syrian hamsters were randomly divided into six groups (n = 12), sham-operated (sham) or ovariectomized (ovx), and kept on the same diet for 120 days to allow for atherosclerotic lesion development. After this 120-day period, whole flaxseed was introduced to the diets of hamsters in three of the groups: group 1 (sham + casein); group 2 (ovx + casein); group 3 (ovx + 7.5% flaxseed); group 4 (ovx + 15% flaxseed); group 5 (ovx + 22.5% flaxseed); and group 6 (ovx + 17β-estradiol). This diet was maintained for an additional 120 days. Lesion regression was examined histologically, and serum was analyzed for total cholesterol, triglyceride, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, Apo A, Apo B, and lipoprotein(a).

RESULTS

Results showed that 15% and 22.5% flaxseed, compared with ovx animals, significantly reduced lipoprotein(a) (4.4 mg/dL [ovx] vs 2.15 mg/dL [15% flaxseed] and 0.3 mg/dL [22.5% flaxseed]; P < 0.05) and Apo B (2.8 mg/dL [ovx] vs 2.4 mg/dL [15% flaxseed] and 2.5 mg/dL [22.5% flaxseed]). Flax reduced by 67% the number of animals with aortic arch lesions.

CONCLUSIONS

All three doses of flax reduce the severity of lesion formation compared with ovx controls. These results support the efficacy of flaxseed in reducing cardiovascular disease risk.

Effects of estrogen on endothelial prostanoid production and cyclooxygenase-2 and heme oxygenase-1 expression

We studied the effects of 17β-estradiol (E₂) (10, 40 nM) on 2 vasoprotective pathways, i.e. cyclooxygenase-2 (COX-2)-dependent prostanoids and the antioxidant heme oxygenase-1 (HO-1), in human umbilical vein endothelial cells (HUVEC) exposed for 6h to steady laminar shear stress (LSS, 10 dyn/cm²), characteristic of atherosclerotic lesion-protected areas. COX-2 was induced by LSS versus static condition (SC). E₂ did not significantly affect COX-2 expression in HUVEC cultured in SC or exposed to LSS. Prostacyclin (PGI₂) and prostaglandin (PG)E₂ were induced while PGF(2α) was reduced by LSS. E₂ caused no effect or a small reduction of prostanoid biosynthesis. In HUVEC cultured in SC or exposed to LSS, E₂ 10 nM caused a comparable HO-1 induction (35-45%) while E₂ 40 nM was 5-fold more potent in LSS-exposed HUVEC than in SC (290% and 58%, respectively). PGI₂ receptor antagonist RO3244794 did not affect HO-1 induction by E₂. In conclusion, E₂ may restrain oxidant stress in the endothelium through HO-1 induction by a mechanism independent on PGI₂ signaling.

The diversity of sex steroid action: regulation of metabolism by estrogen signaling

The metabolic syndrome is a complex condition characterized by obesity, insulin resistance, decreased high-density lipoproteins, and hypertension associated with high risk of developing type 2 diabetes and cardiovascular disease. A major increase in the incidence of developing metabolic syndrome and related diseases is observed worldwide in association with a change toward a less active lifestyle and increased food consumption. Estrogen and the estrogen receptors (ERs) are well-known regulators of several aspects of metabolism, including glucose and lipid metabolism, and impaired estrogen signaling is associated with the development of metabolic diseases. This review will describe the key effects of estrogen signaling in metabolic and glucose sensing tissues, including the liver, pancreatic β cells, adipose tissue, and skeletal muscle. The impact on metabolic processes of impaired estrogen signaling and knock out of each ER subtype will also be discussed.

Estrogen deficiency worsens steatohepatitis in mice fed high-fat and high-cholesterol diet

Recent studies indicate an accelerated progression of nonalcoholic steatohepatitis (NASH) in postmenopausal women. Hypercholesterolemia, an important risk factor for NASH progression, is often observed after menopause. This study examined the effects of estrogen on NASH in ovariectomized (OVX) mice fed a high-fat and high-cholesterol (HFHC) diet. To investigate the effects of estrogen deficiency, OVX mice and sham-operated (SO) mice were fed normal chow or HFHC diet for 6 wk. Next, to investigate the effects of exogenous estrogen replenishment, OVX mice fed with HFHC diet were treated with implanted hormone release pellets (containing 17β-estradiol or placebo vehicle) for 6 wk. OVX mice on the HFHC diet showed enhanced liver injury with increased liver macrophage infiltration and elevated serum cholesterol levels compared with SO-HFHC mice. Hepatocyte monocyte chemoattractant protein-1 (MCP1) protein expression in OVX-HFHC mice was also enhanced compared with SO-HFHC mice. In addition, hepatic inflammatory gene expressions, including monocytes chemokine (C-C motif) receptor 2 (CCR2), were significantly elevated in OVX-HFHC mice. Estrogen treatment improved serum cholesterol levels, liver injury, macrophage infiltration, and inflammatory gene expressions in OVX-HFHC mice. Moreover, the elevated expression of liver CCR2 and MCP1 were decreased by estrogen treatment in OVX-HFHC mice, whereas low-density lipoprotein dose dependently enhanced CCR2 expression in THP1 monocytes. Our study demonstrated that estrogen deficiency accelerated NASH progression in OVX mice fed HFHC diet and that this effect was improved by estrogen therapy. Hypercholesterolemia in postmenopausal women would be a potential risk factor for NASH progression.

Atherosclerosis and sex hormones: current concepts

CVD (cardiovascular disease) is the leading cause of death for women. Considerable progress has been made in both our understanding of the complexities governing menopausal hormone therapy and our understanding of the cellular and molecular mechanisms underlying hormone and hormone receptor function. Understanding the interplay of atherosclerosis and sex steroid hormones and their cognate receptors at the level of the vessel wall has important ramifications for clinical practice. In the present review, we discuss the epidemiology of CVD in men and women, the clinical impact of sex hormones on CVD, and summarize our current understanding of the pathogenesis of atherosclerosis with a focus on gender differences in CVD, its clinical presentation and course, and pathobiology. The critical animal and human data that pertain to the role of oestrogens, androgens and progestins on the vessel wall is also reviewed, with particular attention to the actions of sex hormones on each of the three key cell types involved in atherogenesis: the endothelium, smooth muscle cells and macrophages. Where relevant, the systemic (metabolic) effects of sex hormones that influence atherogenesis, such as those involving vascular reactivity, inflammation and lipoprotein metabolism, are discussed. In addition, four key current concepts in the field are explored: (i) total hormone exposure time and coronary heart disease risk; (ii) the importance of tissue specificity of sex steroid hormones, critical timing and the stage of atherosclerosis in hormone action; (iii) biomarkers for atherosclerosis with regard to hormone therapy; and (iv) the complex role of sex steroids in inflammation. Future studies in this field will contribute to guiding clinical treatment recommendations for women and help define research priorities.

17beta-estradiol prevents early-stage atherosclerosis in estrogen receptor-alpha deficient female mice

Estrogen is atheroprotective and a high-affinity ligand for both known estrogen receptors, ERα and ERβ. However, the role of the ERα in early-stage atherosclerosis has not been directly investigated and is incompletely understood. ERα-deficient (ERα−/−) and wild-type (ERα+/+) female mice consuming an atherogenic diet were studied concurrent with estrogen replacement to distinguish the actions of 17β-estradiol (E₂) from those of ERα on the development of early atherosclerotic lesions. Mice were ovariectomized and implanted with subcutaneous slow-release pellets designed to deliver 6 or 8 μg/day of exogenous 17β-estradiol (E₂) for a period of up to 4 months. Ovariectomized mice (OVX) with placebo pellets (E₂-deficient controls) were compared to mice with endogenous E₂ (intact ovaries) and exogenous E₂. Aortas were analyzed for lesion area, number, and distribution. Lipid and hormone levels were also determined. Compared to OVX, early lesion development was significantly (p < 0.001) attenuated by E₂ with 55–64% reduction in lesion area by endogenous E₂ and >90% reduction by exogenous E₂. Compared to OVX, a decline in lesion number (2- to 4-fold) and lesser predilection (~4-fold) of lesion formation in the proximal aorta also occurred with E₂. Lesion size, development, number, and distribution inversely correlated with circulating plasma E₂ levels. However, atheroprotection was independent of ERα status, and E₂ athero-protection in both genotypes was not explained by changes in plasma lipid levels (total cholesterol, triglyceride, and high-density lipoprotein cholesterol). The ERα is not essential for endogenous/exogenous E₂-mediated protection against early-stage atherosclerosis. These observations have potentially significant implications for understanding the molecular and cellular mechanisms and timing of estrogen action in different estrogen receptor (ER) deletion murine models of atherosclerosis, as well as implications to human studies of ER polymorphisms and lipid metabolism. Our findings may contribute to future improved clinical decision-making concerning the use of hormone therapy.

Estrogen-replacement therapy promotes angiogenesis after acute myocardial infarction by enhancing SDF-1 and estrogen receptor expression

Although observational data suggest that estrogen-replacement therapy (ERT) may confer cardioprotection, estrogen's putative protective role has been challenged. This study investigated the effect of estradiol on peripheral blood stem cells and angiogenesis after acute myocardial infarction and potential mechanisms of estrogen's pro-angiogenesis effect. An ovariectomized rat acute myocardial infarction (AMI) model was established by ligation of the left anterior descending coronary followed by delivery of varying doses of estradiol benzoate. Serum estradiol levels were assessed by radioimmunoassay. Expression levels of alpha and beta estrogen receptor (ER) proteins in myocardium were determined by Western blotting. CD34(+) cells in myocardium at 24 h and in peripheral blood 1, 3 and 7 days after AMI were measured by immunohistochemistry and flow cytometry, respectively. Stromal cell-derived factor (SDF-1) expression and capillary density in myocardium were detected by immunohistochemistry. In ovariectomized rats, ERT significantly increased estradiol levels and up-regulated ER-alpha and -beta expression relative to untreated controls. Furthermore, ERT elevated the number of CD34(+) cells in peripheral blood and myocardium, increased SDF-1 expression, and increased capillary density 4 weeks after AMI. Therefore, our data suggest that estrogen can promote the mobilization and homing of bone marrow stem cells into the myocardium and can increase capillary density in myocardium after AMI. The pro-angiogenesis effect of ERT is associated with enhanced SDF-1 and ER-alpha and -beta expression in myocardium after AMI.

Central estrogen inhibition of angiotensin II-induced hypertension in male mice and the role of reactive oxygen species

It has been shown that reactive oxygen species (ROS) contribute to the central effect of ANG II on blood pressure (BP). Recent studies have implicated an antihypertensive action of estrogen in ANG II-infused female mice. The present study used in vivo telemetry recording and in vitro living mouse brain slices to test the hypothesis that the central activation of estrogen receptors in male mice inhibits ANG II-induced hypertension via the modulation of the central ROS production. In male wild-type mice, the systemic infusion of ANG II induced a significant increase in BP (Delta30.1 +/- 2.5 mmHg). Either central infusion of Tempol or 17beta-estradiol (E2) attenuated the pressor effect of ANG II (Delta10.9 +/- 2.3 and Delta4.5 +/- 1.4 mmHg), and the protective effect of E2 was prevented by the coadministration of an estrogen receptor, antagonist ICI-182780 (Delta23.6 +/- 3.1 mmHg). Moreover, the ganglionic blockade on day 7 after the start of ANG II infusions resulted in a smaller reduction of BP in central Tempol- and in central E2-treated males, suggesting that estrogen inhibits the central ANG II-induced increases in sympathetic outflow. In subfornical organ slices, the application of ANG II resulted in a 21.5 +/- 2.5% increase in ROS production. The coadministration of irbesartan, an ANG II type 1 receptor antagonist, or the preincubation of brain slices with Tempol blocked ANG II-induced increases in ROS production (-1.8 +/- 1.6% and -1.0 +/- 1.8%). The ROS response to ANG II was also blocked by E2 (-3.2 +/- 2.4%). The results suggest that the central actions of E2 are involved in the protection from ANG II-induced hypertension and that estrogen modulation of the ANG II-induced effects may involve interactions with ROS production.

Progesterone Antagonizes the Vasoprotective Effect of Estrogen on Antioxidant Enzyme Expression and Function

Oxidative stress plays an important role in the pathogenesis of atherosclerosis and can be effectively influenced by radical scavenging enzymes. Estrogens exert antioxidative effects in the vasculature; however, cotreatment with progesterone may abrogate the vasoprotective effects of estrogen. Therefore, the effects of progesterone on the production of reactive oxygen species (ROS) and expression and function of antioxidant and oxidant enzymes were investigated in cultured vascular smooth muscle cells (VSMCs) and vascular tissue of mice. Progesterone time- and concentration-dependently downregulated extracellular superoxide dismutase (ecSOD) and manganese superoxide dismutase (MnSOD) expression and enzyme activity and reversed 17β-estradiol–induced overexpression of ecSOD and MnSOD in VSMCs. Nuclear run-on assays revealed that progesterone decreases MnSOD and ecSOD transcription rates. Consequently, progesterone increased ROS release in VSMCs that was prevented by concomitant treatment with 17β-estradiol. Estrogen deficiency in ovariectomized mice was associated with an increase in vascular superoxide release and NADPH oxidase activity. Estrogen replacement prevented this increase, whereas progesterone substitution enhanced ROS production and NADPH oxidase activity. The modulation of superoxide release coincided with decreased expression of ecSOD and MnSOD and upregulation of the p22phox and p67phox subunits of the NADPH oxidase complex in progesterone-treated animals. Furthermore, administration of progesterone to ovariectomized mice treated with 17β-estradiol abrogated the antioxidative effects of estrogen. Progesterone antagonizes the vasoprotective effects of estrogen on ecSOD and MnSOD expression and increases NADPH oxidase activity. These findings may in part explain why hormone replacement therapy with estrogen plus progesterone displayed no beneficial effect on cardiovascular event rates in the prospective clinical trials.

The relationship between sex hormones and lipid profile in men with coronary artery disease

BACKGROUND

Men are more prone to develop coronary artery disease (CAD) than women and the mechanism of this different susceptibility is not well elucidated. The aim of this study was to evaluate the relationship between serum levels of several sex hormones and serum levels of lipoproteins, as well as the association between sex hormones and clinical covariates in men with stable coronary artery disease.

METHODS

Study population consisted of 111 men (mean age 55 years) with stable coronary artery disease. In all patients levels of testosterone, dehydroepiandrosterone sulfate (DHEA-S), estradiol, sex hormone binding globuline (SHBG), luteinizing hormone (LH) and follicle stimulating hormone (FSH) were measured and free testosterone index (FTI) was calculated knowing SHBG. Standard lipid analysis included total cholesterol, HDL-cholesterol, LDL-cholesterol, and triglycerides. The extent of coronary artery disease was defined using semiquantitative coronary angiography score.

RESULTS

Significant positive correlations were found between estradiol levels and levels of total cholesterol (r = 0.31; p = 0.005), LDL-cholesterol (r = 0.32; p=0.004), total cholesterol/HDL ratio (r = 0.26; p = 0.020), and triglycerides (r = 0.24; p = 0.030), whereas no significant association was found between levels of these lipids and testosterone or DHEA levels. HDL cholesterol showed a significant association with levels of FSH (r = 0.23; p = 0.03) and LH (r = 0.25; p = 0.02).

CONCLUSIONS

Our results indicate a possible role of estradiol in promoting the development of atherogenic lipid milieu in men with CAD. Simultaneously, the observed association between increased FSH and LH levels with increased levels of HDL cholesterol might suggest a protective effect of these hormones.

Inhibition of angiotensin II induced endothelin-1 gene expression by 17-beta-oestradiol in rat cardiac fibroblasts

OBJECTIVE

To examine whether 17-beta-oestradiol (E(2)) may alter angiotensin II (Ang II) induced cell proliferation and to identify the putative underlying signalling pathways in rat cardiac fibroblasts.

DESIGN

Cultured rat cardiac fibroblasts were preincubated with E(2) then stimulated with Ang II. [(3)H]Thymidine incorporation and endothelin-1 (ET-1) gene expression were examined. The effect of E(2) on Ang II induced NADPH oxidase activity, reactive oxygen species (ROS) formation, and extracellular signal regulated kinase (ERK) phosphorylation were tested to elucidate the intracellular mechanism of E(2) in proliferation and ET-1 gene expression.

RESULTS

Ang II increased DNA synthesis, which was inhibited with E(2) (1-100 nmol/l). E(2), but not 17-alpha-oestradiol, inhibited Ang II induced ET-1 gene expression as shown by northern blotting and promoter activity assay. This effect was prevented by co-incubation with the oestrogen receptor antagonist ICI 182,780 (1 micromol/l). E(2) also inhibited Ang II increased NADPH oxidase activity, ROS formation, ERK phosphorylation, and activator protein-1 mediated reporter activity.

CONCLUSIONS

The results suggest that E(2) inhibits Ang II induced cell proliferation and ET-1 gene expression, partially by interfering with the ERK pathway through attenuation of ROS generation. Thus, this study provides important new insight regarding the molecular pathways that may contribute to the proposed beneficial effects of oestrogen on the cardiovascular system.

Effect of long-term hormone replacement therapy on coronary endothelial function in postmenopausal women

OBJECTIVES

To determine the difference in endothelial function between premenopausal and postmenopausal women and to determine whether hormone replacement therapy (HRT) is associated with an improvement in coronary endothelial function.

PATIENTS AND METHODS

Women undergoing coronary physiology studies for chest pain at the Mayo Clinic In Rochester, Minn, between December 1992 and April 2002 underwent assessment of coronary endothelium-independent and -dependent function with intracoronary administration of adenosine and acetylcholine, respectively. The coronary diameters, coronary blood flows, and coronary velocity reserves were measured.

RESULTS

A total of 270 women (89 premenopausal and 181 postmenopausal) participated in the study. Endothelium-dependent coronary blood flow change (baseline to peak flow) in response to acetylcholine (10(-4), 10(-5), and 10(-4) mol/L) was lower in postmenopausal women compared with premenopausal women (39.7% vs 72.9%, P = .03). There was no significant difference between the postmenopausal women receiving and not receiving HRT with regard to percent change in coronary diameter (-21.8% vs -13.9%, P = .15), percent change in coronary blood flow (37.3% vs 42.7%, P = .74), or coronary velocity reserve (2.7 vs 2.7, P = .82).

CONCLUSION

This study shows that the postmenopausal state is associated with a greater abnormality in coronary endothelial function at the level of the microcirculation. Moreover, HRT status was not associated with an improvement in coronary endothelial function in postmenopausal women.

Estrogen receptor-alpha mediates estrogen facilitation of baroreflex heart rate responses in conscious mice

Estrogen facilitates baroreflex heart rate responses evoked by intravenous infusion of ANG II and phenylephrine (PE) in ovariectomized female mice. The present study aims to identify the estrogen receptor subtype involved in mediating these effects of estrogen. Baroreflex responses to PE, ANG II, and sodium nitroprusside (SNP) were tested in intact and ovariectomized estrogen receptor-alpha knockout (ERalphaKO) with (OvxE+) or without (OvxE-) estrogen replacement. Wild-type (WT) females homozygous for the ERalpha(+/+) were used as controls. Basal mean arterial pressures (MAP) and heart rates were comparable in all the groups except the ERalphaKO-OvxE+ mice. This group had significantly smaller resting MAP, suggesting an effect of estrogen on resting vascular tone possibly mediated by the ERbeta subtype. Unlike the WT females, estrogen did not facilitate baroreflex heart rate responses to either PE or ANG II in the ERalphaKO-OvxE+ mice. The slope of the line relating baroreflex heart rate decreases with increases in MAP evoked by PE was comparable in ERalphaKO-OvxE- (-6.97 +/- 1.4 beats.min(-1).mmHg(-1)) and ERalphaKO-OvxE+ (-6.18 +/- 1.3) mice. Likewise, the slope of the baroreflex bradycardic responses to ANG II was similar in ERalphaKO-OvxE- (-3.87 +/- 0.5) and ERalphaKO-OvxE+(-2.60 +/- 0.5) females. Data suggest that estrogen facilitation of baroreflex responses to PE and ANG II is predominantly mediated by ERalpha subtype. A second important observation in the present study is that the slope of ANG II-induced baroreflex bradycardia is significantly blunted compared with PE in the intact as well as the ERalphaKO-OvxE+ females. We have previously reported that this ANG II-mediated blunting of cardiac baroreflexes is observed only in WT males and not in ovariectomized WT females independent of their estrogen replacement status. The present data suggest that in females lacking ERalpha, ANG II causes blunting of cardiac baroreflexes similar to males and may be indicative of a direct modulatory effect of the ERalpha on those central mechanisms involved in ANG II-induced resetting of cardiac baroreflexes. These observations suggest an important role for ERalpha subtype in the central modulation of baroreflex responses. Lastly, estrogen did not significantly affect reflex tachycardic responses to SNP in both WT and ERalphaKO mice.

Hormones and coronary atherosclerosis in women

Heart disease is the major health issue facing women in the United States today. Yet, less than 50% of women are aware cardiovascular disease is a health problem. Atherosclerosis begins in childhood and lipid streaks have been identified in girls ages 15-19 in the abdominal aorta and the right coronary artery. Risk factors for cardiovascular disease in women include smoking, diabetes, hypertension, lipid disorders, and menopause. Observational studies have reported a 30-50% reduction in cardiovascular events when estrogen was administered to younger women for menopausal symptoms, yet randomized trials in older patients have failed to show benefit with hormonal replacement therapy. Recent studies have reported preservation of lipid and vascular vasodilatation with low-dose conjugated equine estrogens (CEE) in women and an absence of inflammatory and clotting changes that were observed in high-dose CEE. Recommendations for reducing cardiovascular risk in postmenopausal women include smoking cessation, regular exercise, and weight control. Should hormone therapy be continued beyond management of menopausal symptoms and treatment for osteoporosis, a statin drug should be added to eliminate future cardiovascular complications. Future research will examine low-dose hormonal therapy, earlier administration after menopause, newer agents, and routes of estrogen administration.

Comparison of angiographic findings among postmenopausal women using unopposed estrogen, estrogen/progestin combinations, and nonusers

Studies of the effects of menopausal hormone therapy on coronary artery disease (CAD) in postmenopausal women have provided contradictory results. Although recent experimental studies have revealed no beneficial effect of combination therapy with estrogen (E) and progesterone (P), the effect of monotherapy with E remains unknown. We retrospectively examined the medical records of 843 consecutive women aged > or =55 years who underwent their first cardiac catheterization between January 1996 and December 1998. We compared the presence and severity of CAD, defined as > or =1 diseased coronary vessel (with stenosis > or =50%), in women who only took E, E+P, or no menopausal hormone therapy. In all, 210 women (33%) took hormones, of whom 47 (22%) used E+P and 163 (78%) used E only. Women who used any hormones tended to be healthier than nonusers, but E+P users had a lower prevalence of risk factors and co-morbidities than E users. In unadjusted analyses, both the E and E+P groups were significantly less likely to have CAD than nonusers (relative risk [RR] 0.71, 95% confidence interval [CI] 0.58 to 0.84 for the E group; RR 0.76, 95% CI 0.54 to 0.99 for the E+P group). Demographic factors, CAD risk factors, co-morbidities, and primary prevention medication use explained the association between E+P and the presence of CAD (RR 1.14, 95% CI 0.74 to 1.39). In contrast, adjustment for these factors had a minimal effect on the association between E and CAD compared with nonusers (RR 0.79, 95% CI 0.59 to 0.98). Thus, the apparent protective effect of combination menopausal hormone therapy with E+P on CAD is due to differences in other patient characteristics. In contrast, unopposed E therapy may have a protective effect on CAD.

NO mediates effects of estrogen on central regulation of blood pressure in restrained, ovariectomized rats

We tested the hypotheses that estrogen replacement in ovariectomized (OVX) rats attenuates cardiovascular responses to psychological stress and that nitric oxide (NO) in the brain mediates these effects. Female rats were OVX; one group received 17beta-estradiol (OVX-E) for 11-12 days and the other received vehicle (OVX-V). Seven days after OVX, OVX-E and OVX-V rats were chronically instrumented for arterial pressure measurements and intracerebroventricular injections. Later (4-5 days), OVX-E and OVX-V rats received intracerebroventricular injections of NG-nitro-l-arginine (88 microg/kg), an inhibitor of constitutive NO production, or vehicle. Mean arterial pressure (MAP) and heart rate responses were then measured in conscious rats exposed to two cycles of 1-h restraint/1-h rest. We show that MAP responses in restrained OVX-E rats were attenuated both during restraint and during rest. Although inhibition of NO production in the brain had no effect on MAP responses to restraint in OVX-V rats, it augmented responses in restrained OVX-E rats, especially during periods of rest, so that MAPs in restrained OVX-E and OVX-V rats were indistinguishable. Finally, NO levels in hypothalami and brain stems were elevated in restrained OVX-E, but not OVX-V, rats compared with their respective unrestrained controls. These results show that estrogen replacement in OVX rats reduces arterial pressure responses to psychological stress and that these effects are mediated, at least in part, by NO.

17 beta-Estradiol inhibits angiotensin II activation of area postrema neurons

It is well established that the area postrema, as a circumventricular organ, is susceptible to modulation by circulating hormones and peptides. Furthermore, activation of the area postrema has been shown to modulate central neurons involved in the regulation of cardiovascular function and blood pressure. In particular, the vasoactive peptide angiotensin II (ANG II) has been shown to inhibit baroreflex regulation of heart rate and increase sympathetic outflow and blood pressure via activation of area postrema neurons. Estrogen is thought to protect against hypertension in both humans and animal models and has been shown in a number of systems to alter the effects of ANG II. The purpose of the present study was to determine the effects of estrogen on ANG II activation of area postrema neurons. In this study, the effects of ANG II and KCl on fura 2-measured cytosolic Ca2+ concentration ([Ca2+]i) responses in cultured area postrema neurons in the presence and absence of 12-h exposure to 100 nM 17 beta-estradiol (E2) were evaluated. In neurons incubated in control vehicle media, 50 nM ANG II increased [Ca2+]i by 92 +/- 12%. In neurons preincubated with 100 nM E2, ANG II increased [Ca2+]i by only 68 +/- 11%, for a total inhibition of the ANG II-evoked response of 24%. Coapplication of the estrogen receptor antagonist ICI-182,780 did not inhibit the effects of E2. In the same cells in which the effects of E2 on ANG II-evoked responses were tested, the effects of incubation in E on the depolarization-induced increased [Ca2+2]i due to 60 mM KCl were also tested. Incubation of the cells with 100 nM E increased the KCl-evoked [Ca2+2]i response, and this response was blocked by ICI-182,780. These results suggest that in the area postrema, estrogen may utilize multiple pathways to modulate neural activity and responses to ANG II.

Modulation of antioxidant enzyme expression and function by estrogen

Oxidative stress plays a pivotal role in the pathogenesis of atherosclerosis and can be effectively influenced by radical scavenging enzyme activity and expression. The vasoprotective effects of estrogens may be related to antioxidative properties. Therefore, effects of 17beta-estradiol on production of reactive oxygen species and radical scavenging enzymes were investigated. 17beta-estradiol diminished angiotensin II-induced free radical production in vascular smooth muscle cells (DCF fluorescence laser microscopy). 17beta-estradiol time- and concentration-dependently upregulated manganese (MnSOD) and extracellular superoxide dismutase (ecSOD) expression (Northern and Western blotting) and enzyme activity (photometric assay). Nuclear run-on assays demonstrated that 17beta-estradiol increases MnSOD and ecSOD transcription rate. Half-life of MnSOD mRNA was not influenced, whereas ecSOD mRNA was stabilized by estrogen. Copper-zinc SOD, glutathione-peroxidase, and catalase were not affected by estrogen. Estrogen deficiency in ovariectomized mice induced a downregulation of ecSOD and MnSOD expression, which was associated with increased production of vascular free radicals and prevented by estrogen replacement or treatment with PEG-SOD. In humans, increased estrogen levels led to enhanced ecSOD and MnSOD expression in circulating monocytes. Estrogen acts antioxidative at least to some extent via stimulation of MnSOD and ecSOD expression and activity, which may contribute to its vasoprotective effects.

Estrogen increases bone marrow-derived endothelial progenitor cell production and diminishes neointima formation

BACKGROUND

Estrogens improve endothelial function and accelerate reendothelialization after vascular injury via largely unknown mechanisms. Bone marrow-derived endothelial progenitor cells (EPCs) are thought to positively influence endothelialization, vascular repair, and angiogenesis.

METHODS AND RESULTS

In mice subjected to sham operation, ovariectomy, or ovariectomy and estrogen replacement treatment, estrogen deficiency significantly decreased EPCs circulating in the peripheral blood and residing in the bone marrow, as well as EPCs that were in vitro expanded from spleen-derived mononuclear cells. These effects were completely prevented by estrogen replacement. Human women with increased estrogen plasma concentrations also displayed profoundly increased levels of circulating EPCs. Estrogens increase EPC numbers through a decreased apoptosis rate, which is mediated via a caspase-8-dependent pathway. Estrogen deficiency increased neointima formation after carotid artery injury in mice, but this effect was diminished by estrogen replacement therapy. In mice transplanted with green fluorescent protein-positive bone marrow, reendothelialization of injured vessel segments by bone marrow-derived cells was decreased during estrogen deficiency and increased in response to estrogen treatment.

CONCLUSIONS

Estrogens increase numbers of EPCs by antiapoptotic effects leading to accelerated vascular repair and decreased neointima formation.

Effect of estrogen plus progestin on progression of carotid atherosclerosis in postmenopausal women with heart disease: HERS B-mode substudy

OBJECTIVE

The Heart and Estrogen/Progestin Replacement Study (HERS) found no overall effect of estrogen plus progestin (compared with placebo) on coronary event rates in 2763 postmenopausal women with established coronary disease (mean 4.1 years of follow-up). In addition to the events trial, a carotid ultrasound substudy was established in 1993 to be conducted concurrently to determine whether hormone therapy affects the progression of the underlying atherosclerotic process.

METHODS AND RESULTS

Within the larger HERS, a subset of 362 participants underwent carotid B-mode ultrasound examinations at baseline and the end of follow-up. Progression of carotid atherosclerosis was measured as the temporal change in intimal-medial thickness (IMT).

CONCLUSIONS

IMT progressed in the hormone treatment and placebo groups, although there was no statistical difference between the rates: IMT progressed 26 microm/y (95% CI 18 to 34 microm/y) in the hormone group and 31 microm/y (95% CI 21 to 40 microm/y) in the placebo group (P=0.44). There were also no significant treatment effects when the results were examined by carotid segment or were adjusted for covariates. These data support the American Heart Association recommendation that women with established coronary disease should not initiate hormone therapy with an expectation of atherosclerotic benefit.

Hormone therapy and the cardiovascular system

The cardiovascular effects of female sex steroids have many faces and are very complex. To make this situation even more complicated different disease situations, different target organs and different therapeutic regimens may exhibit different effects of estrogens and progestines. Furthermore, the interpretation of population studies may be problematic by itself, in view of so many confounders and biases involved and methodological flaws that sometimes are discovered only post-hoc. It seems, therefore, that in such a complicated situation making definite conclusions and guidelines is almost an impossible task. My suggestion to clinicians is to try and follow the main stream of clinical data, looking at the general picture rather than the small details, and try to individualize therapy in order to maximize the benefits and minimize the adverse reactions and risks. This article discusses the current knowledge on hormone replacement therapy (HRT) and the cardiovascular system. It is not an overview, because my intention was not to pump in as much data as possible. Rather, the article presents current ideas and trends in this field to be used by people who practice menopause medicine for their own clinical decisions.

The choice of hormone replacement therapy or statin therapy in the treatment of hyperlipidemic postmenopausal women

Evidence based treatment of cardiovascular risk factors on outcome in women is still inconclusive given the very large numbers needed to achieve a significant difference in cardiovascular event. Although numerous studies of the effect of hormone replacement therapy (HRT) on risk factors have suggested benefit, the only data from a randomised control trial of HRT in secondary prevention was neutral. Coronary disease-primary prevention: (a) Statins: Air Force/Texas Coronary Atherosclerosis Prevention Study (AFCAPS/TEX CAPS). The only randomised controlled trial (RCT) to include women. There were fewer coronary heart disease (CHD) events in women but no difference in mortality. (b) HRT: no completed RCT-the results from Womens Health Initiative (WHI) and Women Intervention Study of Long Duration of Oestrogen in the Menopause (WISDOM) are awaited, the former likely to complete in 2004. There are numerous reports of positive observational epidemiological studies for HRT. There is little evidence for statin use in women who will probably not qualify for treatment on global CHD risk assessment, familial hypercholesterolemia and type 2 diabetes excepted. HRT is, therefore, not only appropriate for its multiple effects on lipoproteins, vascular function and insulin sensitivity but also for prevention of osteoporosis. Coronary disease-

SECONDARY PREVENTION

(a) Statins: the major measurable effect of these drugs is to reduce total and LDL cholesterol. In RCT trials, the Scandanavian Simvastatin Survival Study (4S), the Cholesterol and Recurrent Event (CARE) and Long-term Intervention with Pravastatin in Ischaemic Disease (LIPID), approximately 20% of subjects were female, in whom CHD events, but not CHD or total mortality were reduced. (b) HRT: there is data available from a single RCT of continuous combined premarin and medroxyprogesterone acetate (MPA) against placebo, The Heart Estrogen Replacement Study (HERS). A study of 2763 women and mean duration of 4.1 years. This study was neutral, with no reduction in CHD events or mortality. There were more events in the first year, and fewer in years 3-5. Other studies of HRT have been observational and positive for HRT. The effects of treatment on lipoproteins with statins, HRT and combination of statin and HRT have been investigated. In secondary prevention for hyperlipidemic women to achieve cholesterol <5, low density lipoprotein (LDL)<3 mmol/l statins will be first choice, possibly with HRT additionally for its other benefits on cardiovascular risk factors.

Raloxifene improves endothelial dysfunction in hypertension by reduced oxidative stress and enhanced nitric oxide production

BACKGROUND

It has not been completely clarified whether selective estrogen receptor modulators (SERMs) such as raloxifene exert vasoprotective effects similar to those of estrogens.

METHODS AND RESULTS

To investigate vascular effects of raloxifene, male spontaneously hypertensive rats were treated for 10 weeks with either raloxifene (10 mg x kg(-1) x d(-1)) or vehicle. Raloxifene improved endothelium-dependent vasodilatation but had no effect on either endothelium-independent vasorelaxation or phenylephrine-induced vasoconstriction. Raloxifene treatment increased the release of NO from the vessel wall by enhanced expression and activity of endothelial NO synthase. Blood pressure reduction after bradykinin infusion was more pronounced in animals treated with SERMs. The production of superoxide in intact aortic segments was decreased by raloxifene treatment. Administration of raloxifene had no effect on the expression of the essential NAD(P)H oxidase subunits p22phox and nox1 in the vasculature but reduced the activity and expression of vascular membrane-bound rac1, a GTPase required for the activation of the NAD(P)H oxidase. Finally, blood pressure levels were significantly decreased in spontaneously hypertensive rats treated with raloxifene. All SERM effects were also detected in healthy age-matched Wistar rats. In cultured rat aortic vascular smooth muscle cells, raloxifene inhibited angiotensin II-induced reactive oxygen species production dependent on estrogen receptor activation.

CONCLUSIONS

Raloxifene treatment improves hypertension-induced endothelial dysfunction by increased bioavailability of NO. This is achieved by an increased activity of endothelial NO synthase and by an estrogen receptor-dependent reduction in release of reactive oxygen species from vascular cells. These vascular effects cause a profound blood pressure reduction and lead to decreased vascular damage in male spontaneously hypertensive rats.

Ageing is associated with a decrease in the number of sarcolemmal ATP-sensitive K+ channels in a gender-dependent manner

The opening of sarcolemmal K(ATP) channels is considered to be an important endogenous cardioprotective mechanism. On the other hand, age-dependent changes in the myocardial susceptibility to ischemia and hypoxia have been observed in different species, including humans. Here, we have hypothesized that aging might be associated with the changes in sarcolemmal K(ATP) channels. Therefore, the main objective of the present study was to establish whether aging changes expression of cardiac sarcolemmal ATP-sensitive K+ (K(ATP)) channels. RT-PCR using primers specific for K(ATP) channel subunits, Kir6.2, Kir6.1 and SUR2A subunits was performed using total RNA from guinea-pig ventricular tissue. Whole cell electrophysiology was done on isolated guinea-pig ventricular cardiomyocytes. Western blotting using anti-Kir6.2 and anti-SUR2A antibodies was performed on cardiac membrane fraction. Tissue and cells were harvested from young and old, male and female guinea-pigs. RT-PCR analysis did not reveal significant age-related changes in levels of Kir6.1 or Kir6.2 mRNAs. However, levels of SUR2A were significantly lower in old than in young females. Such age-differences were not observed with cardiac tissue from male animals. In both old and young males, pinacidil (100 microM) induced outward currents. The difference between current density of pinacidil-sensitive component in females, but not males, was statistically significant. Western blotting analysis revealed higher levels of Kir6.2 and SUR2A proteins in cardiac membrane fraction from young than old females. The present study demonstrates that in females, but not males, aging is associated with decrease in number of cardiac K(ATP) channels which is due to decrease in levels of the SUR2A subunit.

Postmenopausal hormone replacement therapy as antiatherosclerotic therapy

Cardiovascular disease remains the number one killer of women. Although important for the reduction of cardiovascular events, lipid alteration does not appear to be sufficient to obtain optimum reduction in cardiovascular risk. Women have a potential opportunity for further reduction in cardiovascular risk through postmenopausal hormone replacement therapy. More than 50 observational studies indicate that postmenopausal use of hormone replacement therapy reduces atherosclerosis and cardiovascular events. However, recently reported, randomized, controlled clinical trials have yielded mixed results as to whether hormone replacement therapy reduces cardiovascular events relative to placebo. These, as well as other randomized controlled trials of hormone replacement therapy and cardiovascular disease in postmenopausal women, are reviewed. Although conclusions concerning the specific hormones used in the specific populations studied can be offered from the completed trials, more broad conclusions concerning the use of hormone replacement therapy in the prevention of cardiovascular disease will have to await conduction and completion of other trials.

Reduction of oxidative stress and AT1 receptor expression by the selective oestrogen receptor modulator idoxifene

1. The beneficial vasoprotective effects of oestrogens are hampered by their side effects on secondary sexual organs. Selective oestrogen receptor modulators (SERM) such as idoxifene may exert beneficial vascular effects without influencing cancerogenesis in breast or uterus. 2. In order to investigate vascular effects of selective oestrogen receptor modulators, we examined the impact of idoxifene on production of reactive oxygen species as well as AT1 receptor expression in vascular smooth muscle cells (VSMC). 3. Idoxifene caused a concentration- and time-dependent down-regulation of AT1 receptor mRNA expression, as assessed by Northern analysis. The maximal effect was reached with 10 micromol l(-1) idoxifene after a 4 h incubation period (33+/-7% of control levels). Western blots showed a similar down-regulation of AT1 receptor protein to 36+/-11% of control levels. 4. Confocal laserscanning microscopy using the redox sensitive marker 2',7'-dichlorofluorescein (DCF) and measurement of NAD(P)H oxidase activity in cell homogenates revealed that idoxifene effectively blunted the angiotensin II-induced production of reactive oxygen species. 5. In order to investigate the signal transduction involved in SERM-induced modulation of AT1 receptor expression, VSMC were preincubation with PD98059, genistein, wortmannin, or N(omega)-Nitro-L-arginine. The results suggested that idoxifene caused AT1 receptor down-regulation through nitric oxide-dependent pathways. 6. In conclusion, idoxifene reduces angiotensin II-evoked oxidative stress in VSMC. This could in part be explained by idoxifene-induced down-regulation of AT1 receptor expression. These results demonstrate that the selective oestrogen receptor modulator idoxifene may exert beneficial vascular effects which could be useful for therapeutic regimen in postmenopausal women at risk for cardiovascular diseases.

Human platelets contain a glycosylated estrogen receptor beta

Platelets play an important role in the coronary thrombus formation that leads to myocardial ischemia and infarction. Gender differences in the development of coronary heart disease and its outcomes are partly regulated by estrogen and its receptors, but the roles of the latter in thrombogenicity are less well-defined. We previously demonstrated the presence of estrogen receptor (ER) beta in cells of the megakaryocytic lineage. In this study, we characterize human platelet ERbeta and its expression using biochemical and molecular biological techniques. Western immunoblotting showed that platelet ERbeta migrated with an apparent molecular mass approximately 3.7 kDa larger than ERbeta in a variety of cell lines (including those of prostate and breast origin). A rigorous investigation of platelet ERbeta mRNA by reverse transcriptase-polymerase chain reaction revealed normal transcripts and a single alternately spliced mRNA. However, this variant form was smaller, lacking exon 2, and could not account for the larger protein size seen in platelets. Treatment of ERbeta with N-glycosidase F, which removes core carbohydrate residues, caused a more rapid migration through polyacrylamide gels but had no effect on ERbeta from human cell lines. We conclude that the larger form of ERbeta in human platelets is not attributable to alternate mRNA splicing but primarily to tissue-specific glycosylation.

Estrogen-induced cardiorenal protection: potential cellular, biochemical, and molecular mechanisms

A number of cellular and biochemical processes are involved in the pathophysiology of glomerular and vascular remodeling, leading to renal and vascular disorders, respectively. Although estradiol protects the renal and cardiovascular systems, the mechanisms involved remain unclear. In this review we provide a discussion of the cellular, biochemical, and molecular mechanisms by which estradiol may exert protective effects on the kidneys and vascular wall. In this regard, we consider the possible role of genomic vs. nongenomic mechanisms and estrogen receptor-dependent vs. estrogen receptor-independent mechanisms in mediating the protective effects of estradiol on the renal and cardiovascular systems.

Endothelial dysfunction and oxidative stress during estrogen deficiency in spontaneously hypertensive rats

BACKGROUND

Postmenopausal estrogen deficiency is associated with an increased cardiovascular risk, hypertension, and oxidative stress. Angiotensin type 1 (AT(1)) receptor regulation is involved in the pathogenesis of atherosclerosis. To characterize vascular function, oxidative stress, and AT(1) receptor regulation during estrogen deficiency, ovariectomized spontaneously hypertensive rats (SHR) were investigated in comparison with sham-operated animals and with ovariectomized rats receiving estrogen replacement therapy with 17beta-estradiol.

METHODS AND RESULTS

Arterial blood pressure was similar in all 3 groups investigated. Five weeks after ovariectomy, endothelial dysfunction in aortic rings was observed, which was reversed by estrogen replacement therapy. Estrogen deficiency led to an enhanced vasoconstriction by angiotensin II. Vascular superoxide production was significantly increased compared with that in sham-operated rats, as measured by lucigenin chemiluminescence assays. Estrogen substitution normalized the production of free radicals in the vessel wall. Vascular AT(1) receptor expression was significantly upregulated by estrogen deficiency, as shown by quantitative reverse transcription-polymerase chain reaction, whereas endothelial NO synthase mRNA expression and NO release were unchanged. Five-week treatment of the animals with the AT(1) receptor antagonist irbesartan prevented endothelial dysfunction in ovariectomized rats and normalized the vascular production of free radicals.

CONCLUSIONS

In SHR, estrogen deficiency leads to increased vascular free radical production and enhanced angiotensin II-induced vasoconstriction via increased vascular AT(1) receptor expression, resulting in endothelial dysfunction. Estrogen replacement therapy and AT(1) receptor antagonism prevent these pathological changes. Therefore, estrogen deficiency-induced AT(1) receptor overexpression and oxidative stress may play an important role in cardiovascular diseases associated with menopause.

Estradiol decreases IGF-1 and IGF-1 receptor expression in rat aortic smooth muscle cells. Mechanisms for its atheroprotective effects

Insulin-like growth factor (IGF-1) is a potent mitogen for vascular smooth muscle cells. Both IGF-1 and its receptor have been shown to be highly expressed in atherosclerotic lesions. Here we investigated whether part of the vasculoprotective properties of E(2) may be mediated by its negative regulation of the IGF-1 system. HeLa cells, which do not contain endogenous estrogen receptors (ER), were transiently transfected with IGF-1R promoter constructs with or without a plasmid encoding human ERalpha or ERbeta and treated with 100 nm 17beta-estradiol (E(2)) for 24 h. E(2) treatment decreased basal luciferase activity by 51%, and this effect was dependent on co-expression of ERalpha, whereas no repression was observed with ERbeta. A mutation within the DNA binding domain of the ERalpha abolished the repressor function of the ER receptor. Similarly, E(2) decreased IGF-1R transcription by 21% in rat aortic smooth muscle cells (RASMC), which express endogenous ER. This effect was specific for E(2), because it was inhibited by an antiestrogen and because progesterone did not have any effect on IGF-1R expression in HeLa or RASMC transfected with progesterone receptor. Accordingly, E(2) decreased IGF-1R and IGF-1 mRNA in RASMC by 47% and 33%. Western blot analysis and radioligand binding studies showed that E(2) also dose-dependently decreased IGF-1R protein expression in RASMC by 40% and 30%, respectively, and that IGF-1 protein was reduced by 43%. Repression of IGF-1R promoter activity by a combination of ERalpha and E(2) did not appear to be mediated via direct binding of ER to the IGF-1R promoter but rather by inhibition of SP1 binding to the IGF-1R promoter. Thus, E(2) down-regulates IGF-1R and IGF-1 expression in vascular smooth muscle cells. This may have important implications for the understanding of the beneficial effects of estrogen in the cardiovascular system.

Differential effects of estrogen and progesterone on AT(1) receptor gene expression in vascular smooth muscle cells

BACKGROUND

The beneficial vasoprotective effects of a postmenopausal estrogen replacement therapy may be prevented by a concomitant administration of progestins. To investigate the differential effects of estrogens and progesterone, we examined their influence on AT(1) receptor gene expression in vascular smooth muscle cells (VSMCs).

METHODS AND RESULTS

17beta-Estradiol caused downregulation of AT(1) receptor mRNA expression to 46+/-14%, whereas progesterone led to a significant upregulation to 201+/-29%, as assessed by Northern analysis. Western blots revealed that estrogen induced a downregulation and progesterone an upregulation of the AT(1) receptor protein. Estrogen-induced decrease of AT(1) receptor expression was mediated through activation of estrogen receptors. Nuclear run-on assays revealed that 17beta-estradiol did not alter AT(1) receptor mRNA transcription rate, whereas progesterone caused an enhanced AT(1) receptor mRNA transcription rate. 17beta-Estradiol decreased the AT(1) receptor mRNA half-life from 5 to 2 hours, whereas progesterone induced a stabilization of AT(1) receptor mRNA to a half-life of 10 hours. Preincubation of VSMCs with PD98059, SB203580, herbimycin, wortmannin, or N:(omega)-nitro-L-arginine suggested that 17beta-estradiol caused AT(1) receptor downregulation through nitric oxide-dependent pathways. Progesterone caused AT(1) receptor overexpression via PI(3)-kinase activation. Angiotensin II-induced release of reactive oxygen species was inhibited by estrogens. Progesterone itself enhanced the production of reactive oxygen species.

CONCLUSIONS

Because AT(1) receptor regulation plays a pivotal role in the pathogenesis of hypertension and atherosclerosis, the differential effects of estrogen and progesterone on the expression of this gene may in part explain the potentially counteracting effects of these reproductive hormones on the incidence of postmenopausal cardiovascular diseases.

Enhanced cardiovascular hemodynamics in endurance-trained postmenopausal women athletes

PURPOSE

We sought to determine whether older women athletes who had habitually performed vigorous endurance exercise training had higher stroke volumes and cardiac outputs than sedentary postmenopausal women during maximal exercise.

METHODS

Seventeen endurance-trained, postmenopausal women athletes (age 65 +/- 4 yr; VO2max 2.11 +/- 0.31 L x min(-1), 38.3 mL x kg(-1) x min(-1)) and 14 sedentary, postmenopausal women (age 63 +/- 5 yr; VO2max 1.41 +/- 0.22 L x min(-1), 23.7 +/- 3.5 mL x kg(-1) x min(-1)) performed maximal treadmill exercise while cardiac output (via acetylene rebreathing) and other cardiovascular hemodynamics were measured. Approximately half of the subjects in each group were on hormone replacement therapy (HRT).

RESULTS

The greater VO2max of the athletes was the result of a greater cardiac output (12.8 +/- 1.6 vs. 9.3 +/- 1.4 L x min(-1)) resulting from their significantly larger stroke volume (80 +/- 10 vs 57 +/- 10 mL) at maximal exercise. There were no significant differences in maximal cardiac output or maximal stroke volume related to HRT status in the sedentary women or athletes.

CONCLUSIONS

These data indicate that endurance-trained, competitive, postmenopausal women have higher stroke volumes and cardiac outputs during maximal exercise, than their sedentary peers. However, these data suggest that HRT may not affect maximal CV function in sedentary or endurance-trained postmenopausal women.

Effects of policosanol on postmenopausal women with type II hypercholesterolemia

This randomized, double-blind, placebo-controlled study was conducted to investigate the efficacy, safety and tolerability of policosanol, a cholesterol-lowering drug purified from sugar-cane wax, in postmenopausal women with type II hypercholesterolemia. A total of 244 women who had experienced the menopause and showed elevated serum total cholesterol and low-density lipoprotein cholesterol (LDL-C) levels despite 6 weeks on a standard lipid-lowering diet were randomized to receive placebo or policosanol 5 mg/day for 12 weeks, after which the dose was doubled to 10 mg/day for the next 12 weeks. Policosanol (5 and 10 mg/day) significantly lowered LDL-C levels (17.7% and 25.2%, respectively) and total cholesterol (12.6% and 16.7%, respectively), as well as the ratios of LDL-C to high-density lipoprotein cholesterol (HDL-C) (17.0% and 29.3%, respectively) and total cholesterol to HDL-C (16.7% and 27.2%, respectively), compared to the baseline and placebo; at the same time, policosanol significantly raised HDL-C levels by 16.5% and 29.3%, respectively. The drug was safe and well tolerated. No drug-related adverse events were observed, and even the extent of adverse events was less in the policosanol group than in the placebo group. Four serious adverse events occurred in the placebo group (one myocardial infarction, two cases of hypertensive status and one surgical intervention) compared to none in the policosanol group. In conclusion, policosanol is effective, safe and well tolerated in hypercholesterolemic postmenopausal women.

Clinical profile and long-term prognosis of women < or = 50 years of age referred for coronary angiography for evaluation of chest pain

A significant lack of information exists regarding risk factors, preventive strategies, diagnostic testing, and treatment of women with coronary artery disease (CAD), especially in the young age group. We studied the clinical profile, angiographic results, and long-term follow-up of 135 women aged < or =50 years referred for coronary angiography because of chest pain. The most prominent risk factor was hyperlipidemia (60%), followed by a family history of coronary disease (44%), systemic hypertension (40%), cigarette smoking (31%), postmenopausal state (23%), and diabetes mellitus (21%). Angiographically significant CAD was demonstrated in 79 of 135 patients (58%), most of whom (61%) had 1-vessel CAD. Women with compared to those without significant CAD had a higher prevalence of hyperlipidemia (71% vs 45%; p = 0.002) and of the post-menopausal state (30% vs 16%; p = 0.028). There was no difference in the incidence of positive noninvasive evaluation (ergometry or thallium scan) before catheterization between women with or without significant coronary lesions. At a follow-up period of 2 to 7 years, 3 women had acute myocardial infarction, all of whom demonstrated coronary lesions on prior angiography. No difference was found regarding the recurrence of chest pain on follow-up between women with or without significant CAD. Mortality and congestive heart failure were observed more frequently in women with CAD (6% vs 0%; p = 0.0516 and 12% vs 2%; p = 0.047, respectively).

Hormone replacement therapy and cardiovascular disease

This year's work on hormone replacement therapy (HRT) and cardiovascular disease has been remarkable for the publication of the first randomised controlled trial of HRT use, the Heart Estrogen Replacement Study (HERS). The findings go against not only the trend of previous observational epidemiological studies, but also against findings in the very many studies which have previously shown and continue to show this year a beneficial effect of HRT on a large variety of cardiovascular risk factors, including endothelial function, here reviewed. The aspect of the effect of HRT on clotting variables is clearly crucial given the increased risk of venous thrombosis, and also increased number of cardiac events in the first 4 months of the HERS. Prothrombotic factors increase with age in women, and HRT alters these, particularly fibrinogen, factor VII, and PAI (less change with transdermal HRT) and antithrombin III. In normal women therefore the balance should be towards fibrinolysis rather than coagulation. Work has been presented in abstract for clarifying the effects of HRT on coagulation markers and grasping the problem of differences according to its route of administration. The full publications on this work are expected shortly. We are still awaiting evidence from randomized controlled trials of HRT in primary prevention; one is now recruited but will not report until 2005.

Cardiovascular hemodynamics with increasing exercise intensities in postmenopausal women

We sought to determine the cardiovascular responses to increasing exercise intensities in postmenopausal women with different physical activity levels and hormone replacement therapy (HRT) status. Forty-four women (11 sedentary, 19 physically active, 14 master athletes; 24 not on HRT, 20 on HRT) completed treadmill exercise at 40, 60, 80, and 100% of maximal oxygen consumption. Oxygen consumption, heart rate, blood pressure, and cardiac output, determined via acetylene rebreathing, were measured at each exercise intensity. HRT did not affect cardiovascular hemodynamics. Stroke volume (SV) decreased significantly between 40 and 100% of maximal oxygen consumption in all groups, and the decrease did not differ among groups. The greater oxygen consumption of the athletes at each intensity was due to their significantly greater cardiac output, which was the result of a significantly greater SV, compared with both of the less active groups. The athletes had significantly lower total peripheral resistance at each exercise intensity than did the two less active groups. There were no consistent significant hemodynamic differences between the physically active and sedentary women. These results indicate that SV decreases in postmenopausal women as exercise intensity increases to maximum, regardless of their habitual physical activity levels or HRT status.

Screening for cardiovascular disease. Concepts, conflicts, and consensus

CVD in the United States is prevalent, costly, and disabling. Wherever in the arterial tree atherosclerosis occurs, the process appears to begin in youth, to develop under the influence of the same risk factors, and to be amenable to the same interventions. The relationship between CVD and its associated risk factors is continuous, is graded, and extends below thresholds previously defined as normal. This observation, in turn, is based on an appreciation that in our society, the gap between normal and optimal can be considerable. CVD is a multifactorial process, often related to modifiable lifestyle choices; we focus on any single risk factor to the exclusion of others puts patients in danger. Because risk factors rarely occur in isolation, risk assessment must be as multifactorial as the underlying disease process. By understanding differences between risk factors in terms of the impact of their modification on the underlying disease, targeted interventions become possible that are tailored to the likelihood of an individual patient acquiring CVD. To change the overall prevalence of an epidemic disease such as CVD, however, such a high-risk approach must be applied in concert with a population strategy that seeks to effect smaller degrees of change in the large segment of society that may be at only moderate risk but--because of their great numbers--bears most of the morbidity and mortality of CVD. Finally, despite the remarkable progress that has been made in our understanding of the pathophysiology of CVD and the effectiveness of risk factor modification, significant gaps remain between knowledge and behavior. Fewer than 50% of diabetics are even aware that they have the disease. Only a third of those whose lipid levels qualify them for treatment receive intervention of any kind, including dietary advice. Only 27% of hypertensives have their blood pressure adequately controlled. The potential impact of more vigorous screening practices in the primary care setting on the health of individuals and communities cannot be overstated.

Women's health

Symptoms reliably attributable to menopause are vasomotor symptoms and vaginal dryness. Other symptoms are not directly related to the menopause. HRT or ERT are effective in providing symptom relief and preventing disease prevalent in postmenopausal women. HRT or ERT is beneficial in women with RA. Little data concerns safety in SLE patients, but there are theoretical advantages to using HRT or ERT in women with SLE and two studies that indicate it is safe. Other forms of treatment are available to women who cannot or will not use HRT or ERT.

Localized expression of aromatase in human vascular tissues

The atheroprotective effects of estrogen are well established and the presence of an estrogen receptor in vascular tissues has recently been reported. Therefore, we investigated the localization of the estrogen-producing enzyme aromatase in vascular tissues to assess the possible contribution of endocrine, paracrine, and autocrine modes of action. Aromatase was found in human vascular smooth muscle cells (SMCs) but not in endothelial cells on in situ hybridization. These observations were further supported by quantitative analysis of aromatase mRNA and the activity in 15 human vascular specimens. Only trace levels of expression were detected in the 3 infants examined, whereas 0.0088 to 0.0806 amol/ microg RNA of aromatase mRNA and 12.9 to 122.3 fmol. h-1. mg-1 protein of the activity were detected in 12 of the adult individuals. The switching of tissue-specific exon 1 of the human aromatase gene was also observed in some cases. Aromatase was found to be expressed only in cultured SMCs and not in cultured endothelial cells of human aorta and pulmonary artery and to be regulated through dexamethasone and the signaling pathways of protein kinase A and C. Study results revealed the localized expression of aromatase in vascular SMCs, which indicated a possible direct action of locally produced estrogen in an autocrine or paracrine manner, with possible cross talk between smooth muscle and endothelial cells.

Cardiovascular disease in the diabetic woman

The incidence of cardiovascular disease (CVD) with age is increasing in the United States, and elderly women constitute a disproportional component of the aging population. Elderly women also have a relatively high incidence of diabetes, which contributes to this relatively high CVD risk. Although CVD is less common in premenopausal women than in men, this difference begins to disappear after the onset of menopause, presumably related to decreased levels of female sex hormones (estrogen and/or progesterone). Diabetes mellitus removes the normal premenopausal gender-related differences in the prevalence of CVD by mechanisms that are not clearly defined, including metabolic and hemodynamic factors associated with diabetes. Dyslipidemia in diabetes mellitus consists of low high density lipoprotein cholesterol, elevated triglyceride levels, and a small, dense, more atherogenic low density lipoprotein particle (i.e. oxidized). Dyslipidemia interacts with associated hemodynamic (i.e. hypertension) and metabolic abnormalities (i.e. increased platelet aggregation and plasminogen activator inhibitor-1 levels) to promote CVD risks in diabetic women. Recent controlled trials underscore the critical importance of aggressively treating CVD risk factors, especially dyslipidemia, in women with diabetes.